much harder than it looks at first . . .

Back wires is not necessary even in this puzzle. And, you just need to care about the difference between len(str0) and len(str1), i.e. the value of len(str0) - len(str1) , but NOT THE CERTAIN VALUES OF len(str0) AND len(str1) .

https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2979481698